This invention relates to a radially reciprocating jaw chuck for use on machine tools such as lathes and the like. More specifically, this invention relates to a jaw chuck for machine tools wherein the jaws are self-centering and thereby center the workpiece on the spindle axis.
The prior art is replete with many different constructions for reciprocating jaw chucks, and improvements thereto. One of the more common and least expensive constructions is of the type wherein radial stop screws adjust the radial position of the jaws and clamp the jaws onto the workpiece either internally or externally thereof. Each of the screws is adjusted independently and this type of construction while good for holding the workpiece, can result in inaccuracies in centering the workpiece on the lathe spindle axis.
Another type of jaw chuck is shown in my U.S. Pat. No. 3,658,353 which utilizes master jaws to which work gripping jaws are attached. An axially slideable cam member engages each of the master jaws resulting in simultaneous actuation of each of the work gripping jaws. In such a case, the draw plug actuator is double acting so as to both open and close the jaws of the chuck in a positive manner.
Another prior art type of jaw chuck is shown in U.S. Pat. No. 3,685,844 which utilizes a hydraulically actuated toggle mechanism for opening the jaws, and uses a built in type resilience in master jaws to close the work holding jaws. This type of arrangement however is typically suited only for internal or external gripping, and not both.
All of these prior art types of jaw chucks have advantages and disadvantages in use, but one disadvantage common to all lies in the ability of the chuck to center the workpiece on the center line of the spindle. In the case of a cylindrical workpiece, it is important that the axis of the workpiece in the chuck and the axis of the spindle be colinear. Any deviation from colinearity results in whip in the workpiece with increased wear on the cutting tool and decreased accuracy in the finished product. Additionally, lack of colinearity of the axis of the work and the spindle will result in off-center boring or elliptical turning or other deviations from the desired normal in the machining operation. Accordingly, it is imperative that the workpiece be centered on the spindle axis, and any improvement in the chuck which will facilitate the centering greatly reduces the time and skill required by the operator. Thus, machining costs can be held down by a self-centering type of jaw chuck.
Accordingly, a primary object of this invention is to provide a jaw chuck of the self-centering type.
Another object of this invention is to provide a self-centering jaw chuck of durable yet inexpensive construction.
A further object of this invention is to provide a self-centering jaw chuck which utilizes independent master jaws.
Still another object of this invention is to provide a jaw chuck of extremely high accuracy.
Still a further object of this invention is to provide a jaw chuck with relatively few moving parts.
Still another object of this invention is to provide a self-centering jaw chuck capable of high accuracy when used by an operator possessing lesser skill.
Yet a further object of this invention is to provide a self-centering jaw chuck which utilizes a plurality of master jaws having a fixed portion and a radially reciprocable portion resiliently secured thereto and to which work gripping jaws are attached.